The present invention relates to a fuel injector for supplying fuel directly to a cylinder in an internal combustion engine; and, more particularly the invention relates to a technique using this a fuel injector.
In an internal combustion engine in which fuel is injected directly into a cylinder of the engine, a stratification combustion system has been proposed in which a thick air-fuel mixture is injected in the cylinder in the vicinity of an ignition plug and a thin air-fuel mixture is formed in the area surrounding the ignition plug, so that an improvement in fuel consumption is obtained.
An example of the above-stated internal combustion engine is shown in Japanese application patent laid-open publication No. Hei 6-81651. In the technique described in this publication, a tumble flow is formed in a cylinder, and the injected fuel is directed so as to collide with the piston and be guided by the wall of a cavity portion of the piston. By using this tumble flow technique, the fuel is supported and supplied to the ignition plug.
Further, in Japanese application patent laid-open publication No. Hei 6-81656, a tumble flow is formed in a cylinder and directed in two directions, which include an ignition plug direction from a first fuel injection port of a fuel injector and an ignition plug direction from to a second fuel injection port toward an ignition plug (through immediately under an intake valve and to aim a vicinity immediately under of an exhaust valve and a slight slant lower direction relative to a cylinder direction).
In the above-stated conventional techniques, there is no need to take into consideration adhesion of fuel to a wall face of the piston and a wall face of the cylinder or to the cylinder head, since the fuel adhesion generates to the piston, etc., it is not preferable to reduce a discharge HC (an unburned hydrocarbon) according to an incomplete combustion of the adhered fuel.
The characteristic of a fuel spray injected by a fuel injector and an intake air tumble relate to a combustion characteristic of the internal combustion engine. As to the characteristic of the fuel spray, firstly it relates to the fuel spray shape, and this becomes a factor of the spread angle of the fuel spray and the distance the spray is projected. Secondly, it relates to the fuel spray particle diameter. In this regard, it is necessary to improve the uniformity of the particle distribution by lessening the number of large particles in the fuel spray as much as possible. Thirdly, it relates to the fuel spray structure. In this regard, it is necessary to properly form a spacious distribution of the fuel particles in the fact to be sprayed.
On the other hand, the combustion characteristic of the internal combustion engine also has three main factors. The first factor is to improve ignition performance. For this, it is necessary to provide a large fuel particle distribution in the area surrounding the ignition means and to heighten a distribution of an air-fuel mixture of a combustible concentration and also stay in a long period the air-fuel mixture. Accordingly, an enlargement of the combustion stability range can be attained. Secondly, the fuel particle distribution in the piston direction is made small and the fuel adhesion is restrained; accordingly, the reduction in unburned gas components (HC, CO) of the combustion can be realized. Thirdly, to secure the combustion stability characteristic in a wide region from a low number of engine rotations (engine speed) to a high number of rotations, it is unnecessary to change the fuel spray shape according to a pressure change in the cylinder.
Since a geometric position between the fuel injector and the ignition means is fixed, to always supply a fuel spray having a suitable concentration to the ignition means, it is important to make the spread of the fuel spray constant.
In other words, in the fuel spray which is injected from the conventional fuel injector (for example, an axial symmetric hollow shaped fuel spray obtained by a straight fuel injection port), the fuel spray spreads when the cylinder-in pressure is low, and when the cylinder-in pressure increases, it has a decay in which the fuel spray is crushed and becomes narrow.
In this case, if the cylinder-in pressure is made comparatively high as a standard, when the arrangement between the fuel injector and the ignition means is determined, during the time the cylinder-in pressure is low, fuel adheres easily to a cylinder upper face and a cylinder side face of the cylinder, and to the piston head.
On the other hand, if the cylinder-in pressure is made comparative low as a standard, when the cylinder-in pressure becomes high, there is a decay in which the fuel spray suitable to the combustion will hardly to reach the ignition means.
An object of the present invention is to provide an internal combustion engine wherein a good ignition performance of the internal combustion engine can be obtained.
Another object of the present invention is to provide an internal combustion engine wherein an enlargement of the combustion stability range can be achieved.
A further object of the present invention is to provide an internal combustion engine wherein the discharged amount of unburned gas components of combustion can be reduced.
According to the present invention, in an internal combustion engine comprising a cylinder, a piston, an intake means, an exhaust means, a fuel injector, a fuel supply means, and an ignition means, the fuel injector generates a fuel spray which has a cut out portion, in which the fuel spray is thin in a peripheral direction, as seen in lateral cross-section across a valve axial line of the fuel spray, and injects the cut-out portion in which the fuel spray is thin toward a side of the piston, and the air taken in from the intake means is caused to flow toward a side of the piston of the fuel spray to a side of the ignition plug.
The fuel injector has a large fuel spray angle at the side of the ignition means and a small fuel spray angle at the side of the piston. The fuel injector has an orifice plate, in which a fuel injection hole penetrates the orifice plate in a plate thickness direction, and a fuel spray formation plate for forming the cut-out portion of the fuel spray at an outlet portion of the fuel injector.
The fuel injector generates a fuel spray which has a cut-out portion whereby the fuel spray is thin in a peripheral direction, as seen in lateral cross-section across a valve axial line of the fuel spray, and injects at least two times the cut-out portion in which the fuel spray is thin toward a side of the piston, during one time timing.
Under a state consisting of a high load and a low rotation, during an intake stroke, the fuel is divided into plural parts injected from the fuel injector; and, under a state of a low load and a low rotation, during a compression stroke, the fuel is divided into plural parts injected from the fuel injector.
According to the present invention, a large fuel particle distribution is formed in a surrounding portion of an ignition means, and the distribution of an air-fuel mixture of a combustible concentration is heightened. Also, the air-fuel mixture is retained for a long period. Accordingly, an enlargement of the combustion stability range can be attained.
Further, the fuel particle distribution in the piston direction is made small and the fuel adhesion is restrained; accordingly, the unburned gas components (HC, CO) of the combustion can be reduced. For this reason, as to the fuel spray injected by a fuel injector, the fuel spray angle is made large on the ignition means side, and the fuel spray angle becomes narrow on the piston side. Thus, the and a fuel spray portion having the large fuel spray angle is injected to an opposed side of the piston from a spark generation portion of the ignition means.
At this time, the fuel spray injected from the spark generation portion and directed to the opposed side of the piston can be formed with a good air-fuel mixture having the good combustible concentration by inducing the surrounding air therein.
The change of a fuel spray shape according to a change in cylinder-in pressure is made small, and the combustion stability performance in a wide region from a low engine speed to a high engine speed can be assured. For this reason, a part of the fuel spray cross-section is cut out or cut off, and a pressure difference in an inner portion of the fuel spray and an outer portion of the fuel spray is made small. Accordingly, the fuel spray hardly can be crushed.